Hyaluronic acid (HA) is a mucopolysaccharide found in various physiological fluids, including vitreous humor. The ability of HA to retain water has made it popular as a lubricant or wetting agent in various health care and pharmaceutical compositions, such as ophthalmic, otic, and nasal compositions.
To reduce the likelihood of infection due to microbial growth within compositions administered to an individual, such compositions typically include an antimicrobial preservative. One particularly effective antimicrobial preservative is benzalkonium chloride (BAK). However, it has been observed that HA and cationic preservatives, such as BAK, are incompatible, resulting in their conjugation and precipitation, thereby reducing both the lubricating and preservative properties of the composition. While the loss of such properties may sometimes be overcome by increasing the concentration of one or both compounds, BAK is believed to cause corneal disorders at high concentrations.
Similar precipitation has been noted between BAK and latanoprost. U.S. Patent Application Publication No. 20060069162 to Asada et al. discloses several methods for avoiding such precipitation. These include the addition of a surfactant, the use of a particular species of BAK (i.e., [C6H5CH2N(CH3)R]Cl, wherein R is alkyl having 12 carbon atoms (BAK-C12)), and/or the addition of a nonionic tonicity agent. Such methods are unacceptable, however, as they require the inclusion of additional components to the composition, which increases complexity, expense, and the likelihood of adverse interactions, and/or the restriction of one component to a purified, and more expensive, species.
To this extent, a need exists for preserved compositions containing HA that do not suffer from the defects known in the art.